The present invention relates to a pad construction that is used for padding the human body, such as an insole pad, filled with a material, preferably a wax for conforming slowly to the foot or other body part of a user. The filling is in an envelope which has design features which limit bulging and prevent most peristaltically induced migration of the wax filling. The wax filling moves slowly under weight-bearing forces to form into rather firm concave support surfaces under bony prominences of weight-support areas of the body such as the plantar surfaces of the feet.
In the prior art, a wide range of different types of padded insoles have been used, and the use of various fillings has also been discussed. Insoles have been used which are essentially bladders, having upper and lower layers that are sealed along their edges, and these have been filled with materials such as water, air, and even some that have gum-like elasticity at normal in-door temperatures.
Many of these pads show compartments formed between the layers, so that the materials will flow between compartments as loads change.
It has been observed that old well-worn shoes are preferred by many, in particular Geriatric patients because compaction and wear under the high pressure, bony areas of the foot cause an old shoe to xe2x80x9cwear inxe2x80x9d to a comfortable support contour. However, old shoes do eventually become unserviceable and must be replaced with new ones. There are physiologic reasons why people need better-fitting shoes as they age. Aging muscles will atrophy, and there is a loss of bone mass. These physical changes rob the body of some of its ability to control and absorb shock by deceleration before impact (heel strike) during gait, and such physical changes can often develop into osteoporosis. Loss of flexibility of the joints also affects the body""s ability to adapt to changes in gait cycles or plantar loading. Add the loss of plantar fat pads (located under bony, load bearing prominences of the foot to act as biological shock absorbers), as part of the natural aging process, and the body loses yet another of its defenses against excessive loading on the plantar surface of the foot. All of these changes, combined with a refusal to slow down and accept the coming of age by appropriately adapting lifestyles, can lead to fatigue damage (e.g. strains, bruises, tears of tendons and ligaments, stress fractures, and even the development of worsening of an arthritic condition).
People with one or more of the foot problems just described will find it difficult to tolerate new pairs of prior art shoes, claiming the new shoes are not as comfortable as the old shoes. New shoes typically are uncomfortable for these people until many months of wear have generated concave support contours under bony prominences of the foot. Thus, there is a need for an insole that will provide the custom contoured footbed of the old shoes, after a minimal number of gait cycles, while being worn in the new shoe. By providing this quick footbed break-in for the shoe, comfort can be had with new shoes that provide good support from the last, good ground contact with the new outsole, with the contoured footbed surface from the insole molded or formed to fit the dynamic contours of the owners"" feet.
The present invention relates to a pad for supporting a portion of a human body. The pad has an envelope formed by two overlying layers of strong, high tensile elastic modulus material. The layers of material are sealed along the edges to form a sealed interior compartment. To control peristaltically induced migration of filling material, the pads are preferably further joined at spaced locations, or compartmentalized to form sealed capsules by seams joining the layers within the perimeter of the pad. To control the degree/thickness of bulging within each of the inner sealed capsules, the envelope material layers may be joined in various configurations within the perimeter of those envelopes. The layers forming the envelope can be quilted, or joined in spots or with short pier like seams or darts, which means small area portions of the layers are fused or adhered together in a particular selected pattern to control envelope volume and limit movement of the filling material into the bulged areas as wax is squeezed out of the higher pressure areas under bony prominences. Uncontrolled bulging would allow the concave support surface to have an excessively large, central area where all the filler is pushed out. Such a contour would not spread support loadings as well. Also, it is important to limit envelope thickness for reasons of comfort.
The layers forming the pad envelope should be of a material with a tensile modulus high enough so they stretch very little under the loads imposed by this application. This is necessary so that control of the bulging, thickness and material flow is possible. Any bulging should not be the result of substantial stretching of the pad envelope material.
The filling material is preferably a wax material that does not flow immediately upon first loading, but will shift slowly under repeated applications of weight in a particular area. The slow movement or migration of the wax occurs particularly when the wax is near the temperature of human bodies and under repeated dynamic loads typical during gait. More rapid conforming can be achieved if the wax is preheated. The wax is chosen so that it will be plastic and will flow gradually with many load repetitions but yet be hard or firm and shape retaining when it reaches a location where the supported load, that is, the pressure on an area of the wax, is fairly uniform, and the pad envelope construction is preventing further shifting. The wax, while plastic, does not quickly flow under changes of pressure.
The pad compartments or capsules are chosen to keep the filling in particular areas of the pad and contain and control excessive peristaltic movement of the filling. The slow plastic flow or movement can be controlled by the xe2x80x9cquiltingxe2x80x9d or short xe2x80x9cpierxe2x80x9d seams that are disclosed. Barrier seams are used to form capsules sized to keep the wax filling material from being excessively xe2x80x9cpumpedxe2x80x9d by peristaltic type action under the foot as forceful contact proceeds usually posterior to anterior and lateral to medial during the typical weight bearing cycle of gait, and to maintain a local degree of filling that will conform to the supported surface. Capsule size and design is of particular importance to distribute pressures under irregular surfaces with bony prominences, such as the metatarsal phalangeal (MTP) joint region of a foot.
Further, pad regions, such as the metatarsal-phalangeal (MTP) joint area of an insole have a greater number of compartments or capsules and quilting junctions, so that a support thickness of the wax material in high pressure or bony areas is maintained.
The spacing of the quilting junctions between the top and bottom layers in particular capsules can be modified to regulate the maximum bulge thickness and volume of a compartment or capsule that is closed off by seams between the top and bottom pad layers.
The upper surface of the pad is preferably a low friction material, such as a Teflon(copyright) coated fabric in bony high pressure areas.
The filling material is selected so that the material will redistribute to form a cradle-like support surface only upon repeated applications of loads, such as when walking, to achieve a custom contour under the foot. A firm/bony convexity of the foot will cause a concavity in the filling material, such as wax, so that the foot bears weight on an increased area. However, again, the compartment or capsule has to be sized for volume control, so that there is material supporting the convexity such as a bony protuberance, by filling around it, to better spread the loads on the skin across the supported area.
The present construction deals with control of bulging of the wax material, so that the forming is such that excessive build-up of material in local areas, and an absence of material in other areas that need support is prevented. The spaced quilting or junctions within the compartments or capsules that are formed by seams serve a combination of functions. They prevent excessive amounts of filler material from being squeezed into low pressure areas from under the higher pressure bony areas. Excessive expulsion of filler material from those areas would leave excessively large xe2x80x9cbottomed outxe2x80x9d areas in the center of the cradles. That would reduce their load-spreading capability. Also excessively thick bulging in the lower pressure areas may be uncomfortable on even a barrier to the entry of the toes into the toe box of a shoe.
The filling material, which, again, is preferably a wax, has the potential to flow or redistribute only a little bit with each step. For example, say approximately 50 to 200 steps on an insole will cause the wax, acting like a truly plastic material to adequately redistribute from a uniform thickness to a multiplicity of little hills, hollows, ridges and valleys. As the pressure is equalized, because the filler material is constrained within the compartment or capsule, the material will cease to flow and will provide a firm cradle of broader support under bony areas.
Since the pad envelope material is not easily stretched, the volume of a bulged area of the capsule is fixed. A given capsule is likely to have one or more areas from which much of the wax has been expelled. The wax is pushed out because those areas lie under bony locations of the foot which tend to generate high dynamic pressures during gait. The wax thus pushed out of those areas migrates to the perimeter of those bony prominences causing the capsule to bulge. However, the high tensile modulus of the envelope material in combination with the envelope quilting or junctions limits such flow.
The pressure supporting the body portion on an individual compartment may be different from that provided by another compartment or capsule because the material is constrained. In other words, there is not necessarily an even pressure throughout the entire pad.
Additionally, the filling should have limited thickness, and as part of the volume control, there is a limitation of the bulges of the pad to certain regions or compartments.
While the preferred embodiment is shown as an insole, it can be used as a prosthesis pad to support bony areas of residual limbs. The bony area will move the filling material, such as wax, to spread the pressures that are encountered more evenly than foams.